Conventionally, a heat exchanger includes a core part in which tubes and corrugated fins are alternately stacked with each other, and a header tank joined to the end of the tube in the longitudinal direction to communicate with the tube. The header tank has a core plate to which the tube is inserted and joined, and a tank body which forms the interior space of the header tank with the core plate. The side end of the tank body is fixed to the core plate. The core plate includes a tube junction portion with a flat surface on the inner side of the header tank and a tube insertion hole in which the tube is inserted, and a groove portion defined on the outer side of the tube junction portion to accept the side end of the tank body.
In this kind of heat exchanger, it is known that a seal component (for example, seal ring) is arranged in the groove portion of a core plate, and that the seal component is supported between the bottom of the groove portion and the side end of the tank body (for example, refer to Patent Literature 1), so as to secure the sealing property inside of the header tank.